Complex FEM Based System of Computer Codes to Model Nuclear Fuel Rod Thermo-Mechanical Behavior

Modeling of the thermo-mechanical behavior of the nuclear fuel rod allows to assess the temperatures and stresses that can be used to determine if the fuel rod will operate without failures during proposed steady state conditions and permitted power ramps and also during unexpected power excursions. The paper presents long-term effort to establish closed chain of computer codes, which allow computer modeling of the thermo-mechanical fuel rod behavior from the one dimensional (1D) representation to the 3D detailed problem description. The whole complex uses the same finite element method (FEM) based mathematical approach. The principle of this modular approach is to handle boundary and initial conditions by the similar transfer independent on the complexity of solved problem. We have combined the integral code to the full 2D (r-z) global model of fuel pin ending at 2D (r-z, r-φ) and 3D local detailed submodels. The system of codes is connected (coupled) by data transfer. All the submodels are stand-alone. The same is valid for the material data properties. Examples of simulations results of all the described modeling levels are documented by figures.